Representatives from the five unions gave BBC managers an ultimatum that unless planned changes to the scheme were dropped by 21 July – and assurances given about the protection of the value of pensions already earned – thousands of BBC staff would be balloted for strike action.

The shot across the corporation’s bows comes two weeks after the NUJ claimed BBC employees working in Cardiff, Birmingham and at TV Centre in London were already committed to balloting on strike action over changes to their pensions.

In addition, the threat comes just days after it emerged that deputy director general Mark Byford had already amassed a pension pot worth £3.4 million, one of the biggest ever seen in the public sector.

Jeremy Dear, NUJ general secretary, said: “While managers can look forward to gold-plated pensions, thousands of BBC staff will be left significantly worse off in retirement.

“The BBC has broken its promises to staff and is undermining the value of people’s pensions.

“The BBC must withdraw these proposals or face the prospect of widespread strike action and industrial unrest over the coming months.

“We remain committed to finding a negotiated settlement to address the BBC’s pension shortfall – but not at the expense of the value of pensions already earned.”

The BBC released details last month of its planned pensions overhaul to tackle a £2bn deficit in the fund. Proposals include closing the final-salary scheme to new joiners and capping contributions of existing members.

Staff at the BBC have also been angered by a below-inflation flat rate pay increase of £475 for staff paid up to £37,726 a year.

A BBC spokeswoman told Press Gazette: “We know that staff have concerns about the proposed changes to the pension scheme, and we will listen and try to address these during the consultation period.”